1. Field of the Invention
The present invention relates to a method of manufacturing an ink-jet printhead, and more particularly, to a method of manufacturing a monolithic ink-jet printhead having an ink passage that is monolithically formed on a silicon substrate.
2. Description of the Related Art
In general, an ink-jet printhead is a device printing a predetermined color image by ejecting small droplets of printing ink onto a desired place of a recording sheet.
The ink-jet printhead may eject ink using an electro-thermal transducer (bubble jet-type ink ejection mechanism) which generates a bubble in ink using a heater, or using an electromechanical transducer, which causes a volume variation of ink by a deformation of a piezoelectric device.
The bubble jet-type ink ejection mechanism will be described in greater detail. When power is supplied to the heater having a resistance heating element, ink disposed adjacent to the heater is rapidly heated to a temperature of about 300xc2x0 C. In such a case, the bubble is generated in the ink and expanded to apply pressure to the ink filling an ink chamber. As a result, the ink near a nozzle is ejected from the ink chamber through the nozzle.
FIGS. 1A and 1B are examples of a conventional bubble jet type ink-jet printhead, and give an exploded perspective view showing a structure of the conventional bubble jet type inkjet printhead disclosed in U.S. Pat. No. 4,882,595 and a cross-sectional view illustrating a method of ejecting an ink droplet in the conventional bubble jet type ink-jet printhead, respectively.
Referring to FIGS. 1A and 1B, the conventional bubble jet-type ink-jet printhead includes a substrate 10, a barrier wall 38 installed on the substrate 10 to form an ink chamber 26 filled with ink 49, a heater 12 installed in the ink chamber 26, and a nozzle plate 18 in which a nozzle 16 is formed through which an ink droplet 49xe2x80x2 is ejected. The ink chamber 26 is filled with the ink 49 through an ink channel 24 from an ink supply manifold 14 connected to an ink reservoir (not shown), and the nozzle 16 connected to the ink chamber 26 is filled with the ink 49 by capillary action. A plurality of nozzles 16, a plurality of heaters 12 corresponding to the plurality of nozzles 16, and the ink chambers 26 are arranged in columns adjacent to the ink supply manifold 14 or in columns at both sides of the ink supply manifold 14.
In the above structure, when current is supplied to the heater 12, the heater 12 generates heat to form a bubble 48 in the ink 49 filling the ink chamber 26. After that, the bubble 48 is expanded to apply pressure to the ink 49 and push the ink droplet 49xe2x80x2 out of the ink chamber 26 through the nozzle 16. New ink 49 is sucked through the ink channel 24 to refill the ink chamber 26.
However, in order to manufacture the conventional printhead having the above structure, the nozzle plate 18 and the substrate 10 should be separately manufactured and bonded to each other, resulting in a complicated printhead manufacturing process, and causing a misalignment of the nozzle plate 18 and the substrate 10 when the nozzle plate 18 is bonded to the substrate 10.
Thus, recently, in order to solve the above problems, an ink-jet printhead that is monolithically formed on a silicon substrate has been suggested. The printhead is usually manufactured by using semiconductor device manufacturing techniques such as deposition of material layers, photolithography, and etching. These techniques prevent the misalignment between elements of the printhead, and since they are based on conventional semiconductor device manufacturing processes, the printhead manufacturing process might be simplified, and mass production is facilitated.
As an example of a printhead that is monolithically formed on a silicon substrate, another structure of the conventional ink-jet printhead disclosed in European Publication Patent No. EP 1 078 754 A2 is shown in FIG. 2.
Referring to FIG. 2, a plurality of thin material layers 52, 54, 56, and 58 are stacked on a silicon substrate 50. A resistor layer 70 for heating ink is formed between the material layers 52, 54, 56, and 58. The material layers 52, 54, 56, and 58 and the resistor layer 70 are formed by oxidation of a surface of the silicon substrate 50, deposition of a predetermined material on the silicon substrate 50, and etching using an etch mask formed by photolithography. An ink feed hole 74 is formed to perforate the material layers 52, 54, 56, and 58. The ink feed hole 74 is formed by dry or wet etching the material layers 52, 54, 56, and 58 after forming the etch mask on the material layers 52, 54, 56, and 58 by a photolithographic process. An ink supply manifold 72 is formed by dry or wet etching a rear side of the silicon substrate 50. An orifice layer 60 defining a nozzle 78 and an ink chamber 76 is formed on the material layers 532, 54, 56, and 58. The orifice layer 60 is formed by coating a photoresist on the material layers 52, 54, 56, and 58 through lamination, screen printing, or spin coating, and the nozzle 78 and the ink chamber 76 are formed by the photolithographic process.
As described above, in the ink-jet printhead having the structure shown in FIG. 2, elements constituting an ink passage on the silicon substrate 50, that is, the ink supply manifold 72, the ink feed hole 74, the ink chamber 76, and the nozzle 78 are formed through photolithography and/or etching, and thus the ink-jet printhead having the structure shown in FIG. 2 might have the advantages described above.
However, according to the conventional method of forming the ink passage described above, the ink passage is formed by a dry etching technique, such as reactive ion etching or inductively coupled plasma etching, or by a wet etching technique using KOH and TMAH. Dry etching is mostly anisotropic etching, and since it is difficult to process the ink passage having a complicated internal structure, there are limitations in a processing depth of the ink passage, and a processed surface of the ink passage is also rough. In addition, undesired portions are etched, and since the etch mask must be formed by the photolithographic process, a processing time and a manufacturing cost of the ink-jet printhead increase. In the case of wet etching, the processed surface is comparatively flat, but the etching process easily etches other materials as well as silicon, and thus, it is difficult to selectively etch only a desired portion, and the etching time is extended compared to the dry etching.
As described above, according to the conventional method of manufacturing a monolithic ink-jet printhead using dry etching and wet etching in consideration of a shape and size of the ink passage, the wall of the ink passage is comparatively rough, and it is difficult to precisely adjust the size of the ink passage to a design dimension.
To solve the above and other problems, it is an object of the present invention to provide a method of manufacturing a monolithic ink-jet printhead, the method particularly including reprocessing an internal side of the ink passage using XeF2 gas after forming the ink passage on a silicon substrate.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided a method including forming an ink passage on a silicon substrate, the ink passage having a manifold supplying ink, an ink chamber receiving the ink from the manifold, an ink channel connecting the manifold to the ink chamber, and a nozzle through which the ink is ejected from the ink chamber.
In the method of manufacturing the printhead according an embodiment of the present invention, the ink passage is reprocessed using XeF2 gas after the ink passage is formed on the silicon substrate.
Since the XeF2 gas does not react with any material other than silicon in an etching process using the XeF2 gas, the XeF2 gas has much higher selectivity to silicon than silicon nitride, silicon oxide, photoresist or aluminum. Thus, using the XeF2 gas in the reprocessing of the ink passage allows only the silicon substrate having a wall defining the ink passage to be etched without affecting other material layers.
An equation of the XeF2 gas and silicon is below:
2XeF2+Sixe2x86x922Xe+SiF4.
In the above equation, when the XeF2 gas contacts the silicon substrate, the silicon (Si) on the surface of the silicon substrate chemically reacts with the XeF2 gas to form SiF4. The SiF4 can be separated from a surface of the silicon substrate, and thus the surface of the silicon substrate can be etched to a predetermined depth.
The surface of the silicon substrate etched by the XeF2 gas becomes smooth compared with other dry or wet etching methods. Thus, walls of the ink passage can be smoothed in an operation of reprocessing the ink passage.
In addition, since only XeF2 gas is used and plasma is not used in the operation of reprocessing the ink passage, an electric circuit is not damaged by electric and magnetic influence.
The XeF2 gas has a property of isotropic etching only on the silicon substrate without effect on a crystal orientation of other material layers. Thus, since the walls of the ink passage having a complicated structure can be uniformly processed in an operation of forming the ink passage, a size of the ink passage can be more precisely adjusted to a design dimension.
In addition, a shape (surface) of the ink passage slopes when the XeF2 gas is properly controlled. That is, in the operation of reprocessing the ink passage, the wall of the ink channel can be reprocessed to slope so that a cross-sectional area of the ink channel becomes narrower from the manifold to the ink chamber. As a result, a supply speed of the ink can be increased, and a back flow of the ink can be prevented. This is possible by controlling a flow speed of the XeF2 gas.
Meanwhile, according to an aspect of the present invention, the forming of the ink passage includes forming a membrane layer in which a plurality of material layers are stacked on the silicon substrate, forming the nozzle by etching the membrane layer to a predetermined diameter, forming the ink chamber by etching the silicon substrate exposed through the nozzle, forming the manifold by etching the rear side of the silicon substrate, and forming the ink channel by etching the silicon substrate between the ink chamber and the manifold.
Here, according to another aspect of the present invention, the forming of the membrane layer includes forming an insulating layer on the surface of the silicon substrate, forming a heater surrounding the nozzle on the insulating layer and forming a first passivation layer for protecting the heater on the insulating layer and the heater, and forming an electrode to be electrically connected to the heater on the first passivation layer and forming a second passivation layer for protecting the electrode on the first passivation layer and the electrode.
According to yet another aspect of the present invention, the forming of the ink chamber includes isotropic dry etching the silicon substrate through the nozzle to form a hemisphere of the ink chamber.
In the method of manufacturing a monolithic ink-jet printhead, the ink passage of the ink-jet printhead that is monolithically formed on the silicon substrate is reprocessed using XeF2 gas, smoothing the walls of the ink passage, more precisely adjusting the size of the ink passage to the design dimension, and improving a performance of the printhead.